Forth: Use 'I' as its value with 'CHAR'

Question

I try to use special loop variable I with [CHAR]. With this minimal example:

: ex ( -- )
    10 0 DO
    [CHAR] I EMIT
    LOOP
;

I expected '0123456789' to be printed but -obviously- I get 'IIIIIIIIII'

Is there a way to replace I with its value before [CHAR] gets executed?

No. Instead, to convert a value in the range 0-9 to the ASCII character code for the corresponding digit, add 48: I 48 + EMIT — dave_thompson_085
– dave_thompson_085, Commented Dec 14, 2024 at 11:24
@dave_thompson_085 I can't believe I didn't think about this! Thx. — david
– david, Commented Dec 14, 2024 at 12:48

ruvim · Accepted Answer · 2024-12-15 08:45:21Z

3

[CHAR] X is a character literal, that is represented by a code point of "X" on the stack. The expression [CHAR] X always produces the same value on the stack.

If you want to print "1" given number 1 on the stack, you should get the code point of "1" at the first. You can do it as [char] 0 +.

So you example becomes:

: ex ( -- )
    10 0 DO
        I  [CHAR] 0 +  EMIT
    LOOP
;

answered Dec 15, 2024 at 8:45

ruvim

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1 Comment

david Over a year ago

Great answer! I would have accepted @dave_thompson_085's answer if he had offered one rather than a comment.

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